PROJECT SUMMARY (ABSTRACT) NRAS-mutant cutaneous melanoma is the most aggressive genetic subtype of this disease and has the worst overall prognosis. While NRAS is one of the most commonly mutated genetic drivers of cutaneous melanoma, drugs that effectively target mutant NRAS have yet to be developed. For decades, NRAS has been touted as an ?undruggable? oncogene because the protein lacks a traditional, deep drug binding pocket. Furthermore, therapies targeting post-translational modifications, interacting partners, and signal transduction pathways downstream of NRAS are invariably circumvented by oncogenic variants. Mutations in NRAS primarily alter codons 12, 13, and 61, leading to constitutive protein activation and signaling. However, there appears to be a preference for specific NRAS alterations in each human tumor type. For example, NRAS-mutant melanomas are enriched for genetic alterations in codon 61 (>80%) while acute myeloid leukemias exhibit a preference for mutations affecting codons 12 and 13. This mutational bias remains poorly understood, especially in melanoma where codon 61 alterations cannot be attributed to ultraviolet light. I hypothesize that only NRAS oncogenes found commonly in melanoma (Q61 -R, -K, and -L) possess the functional properties required to efficiently drive melanoma formation. To test this hypothesis, I generated a suite of conditional, NRas knock-in mice (LSL-Q61R, -K, -L, -H, -P, and ?Q; LSL-G12C and ?D; LSL-G13D and -R) and crossed these animals to a melanocyte-specific Cre. Preliminary data from a subset of these genetically engineered mouse models (GEMMs) indicate that the melanomagenic potential of each NRas allele parallels the frequency of that allele in human melanoma. Here, I will employ our full suite of knock-in GEMMs to elucidate the melanomagenic potential of these ten, distinct NRas oncogenes (Aim 1). Capitalizing on these results as well as our preliminary data, preferential effector usage amongst NRas mutants will be explored using BioID (Aim 2). Furthermore, in vitro transcriptomic and phosphoproteomic analyses employing melanocytes isolated form these GEMMs will identify mutation-specific alterations in NRas signaling required for melanoma formation (Aim 3). Completion of these aims will identify melanoma-specific tumor vulnerabilities downstream of oncogenic NRAS and enhance our understanding of the evolution of this challenging disease. To advance my development as an independent scientist I have generated a comprehensive training plan including, but not limited to the following activities: oral presentations, scientific writing, undergraduate mentoring, multi-dimensional data analysis, instruction in murine tumor pathology, external collaborations, and Responsible Conduct in Research training. Presentations at project-relevant meetings and interactions with my dissertation committee will foster feedback from the scientific community to enhance the long-term impact of this work.